Anonymous asked in Science & MathematicsEngineering · 1 decade ago

What minimum kilowatt electric power is required to move and operate a 5-hp electric motor with full load.?

And what is the normal operating ratio between a generator running an electric motor in terms of kilowatt and horsepower ratings or strength without overloading or tripping the generator with the motor running in full load.

4 Answers

  • EE68PE
    Lv 6
    1 decade ago
    Best Answer

    The minimum power requirement would be given by the conversion of the units. One horsepower is equal to 746 watts; 5hp = 3.73 kW. A good 5 hp, 3 phase motor should be at least 84% efficient. That means that the actual power requirement would be about 3.73/0.84 = 4.44 kW.

    A generator running a motor needs to be able to produce enough current to start the motor and accelerate it to full speed. That will require a peak current of something like 600% of the normal operating current. It may take several seconds for the current to fall to the normal level. The generator will have some short term overload capacity, but it may need to be somewhat larger than the 4.4 kW or so required for continuous full load motor operation.

    Source(s): 40 years of related electrical engineering experience
  • 1 decade ago

    In addition to translating hp to kW (first answer) and then converting output power to input power (second answer), you also have to account for the inductive power required to turn the motor. When you add all of this together it comes out to almost a 1 hp = 1 kVA. That is the value my utility uses estimate the demand that most motors create. So on a practical basis you need a generator capable of providing at least 5 kVA to run your 5 hp motor.

    Source(s): 35 years utility experience
  • 4 years ago

    Yes. Hopefully, though, your science lab is too sophisticated to have a simple bar magnet, some wire, and a fan blade. Mount the fan blade on an axle of some sort: pencil, broom handle, etc. Mount the axle on some sort of support so it can turn freely. Mount the magnet on the axle at a right angle. Place a coil of wire a millimeter or so away from the path of the magnet's poles. As the wind turns the fan, it'll turn the the north and south poles of the magnet past the coil, creating a voltage. Use this voltage to turn a small motor. You might need a diode or bridge rectifier (found in the electronics lab, not the science lab) to convert AC to DC for a small DC motor such as is found in many toys.

  • Mαtt
    Lv 6
    1 decade ago

    1 hp = 746 W = 0.746 kW

    5 hp = 3.73 kW,

    There will of course be an additional power draw during the start up, especially if the motor is heavily loaded.

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